PDA vs. Smartphone
It's generally considered that smartphones have won the battle and you will have trouble finding a dedicated PDA nowadays. But have they really won? I think not. What is a smartphone, if not a PDA with a built-in phone? Making phonecalls is just a tiny part of the package! So what happened is not the death of the PDA but rather a merger. This is good because we don't have to carry two separate devices anymore and it's cheaper too. Would the phones eventually evolve to what they are now without the invention of the PDA? Who knows?